Pope Honorius I

Pope Honorius I (died 12 October 638) was the bishop of Rome from 27 October 625 to his death. He was active in spreading Christianity among Anglo-Saxons and attempted to convince the Celts to calculate Easter in the Roman fashion. He is chiefly remembered for his correspondence with Patriarch Sergius I of Constantinople over the latter's monothelite teachings. Honorius was posthumously anathematized, initially for subscribing to monothelitism, and later only for failing to end it. The anathema against Honorius I became one of the central arguments against the doctrine of papal infallibility.